Rear-projection displays (RPDs) have become a popular technology for applications where a self-contained, large-screen display is required, for example rear-projection televisions (RPTs). RPTs are generally available with larger screen sizes than cathode ray tube (CRT) displays due to limitations inherent in the manufacture of large CRTs. More recently, RPDs have also found increased popularity for use in smaller applications, such as monitors.
An RPD includes many individual components that cooperate to display an image for a viewer. For example, a typical RPD has a body or cabinet housing a translucent screen, a light valve, light source, and projection optics. The light source illuminates the light valve, which modulates the light based on image data provided from an input device. The projection optics then project the image output from the light valve onto the screen for display.
During operation the components of an RPD create a significant amount of heat within the cabinet. This heat may cause a number of things to happen that ultimately affects the quality of the image of the light valve displayed at the screen. Increased heat may cause thermal drift between the system components due to physical expansion/contraction of the chassis that holds the components relative to one another. Heat may also have a thermalizing effect on the shape and/or index of refraction of lens elements of the projection optics.
Many design attempts have been presented in the prior art to try to mitigate the effects of thermal cycling within projection systems. One example includes a heater to preheat the components prior to operation in order to create a thermally constant environment. Another example consists of a design of combinations of positive and negative lens elements in an attempt to compensate for the thermalizing effect. However, any mitigative effect provided by these prior art designs falls short of compensating for the thermal cycling experienced throughout the life cycle of a typical projection system.